how to fix P0300 misfire in BMW 3 Series F30/F31 (2012-2019)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before working on it.

2. Check and Replace Spark Plugs

• Remove the engine cover if applicable.
• Using a spark plug socket, carefully unscrew and remove each spark plug.
• Inspect the spark plugs; replace any that are worn or damaged.
• Install new spark plugs, ensuring the correct gap (typically around 0.028-0.032 inches for BMW).
• Torque the spark plugs to the manufacturer’s specifications (usually around 18-22 Nm).

3. Inspect and Replace Ignition Coils

• Disconnect the electrical connectors from each ignition coil.
• Remove the ignition coils using a socket and ratchet.
• Inspect for cracks or damage; replace any faulty coils with new ones.
• Reinstall the ignition coils and reconnect the electrical connectors, ensuring they click into place.

4. Fuel System Check

• Connect a fuel pressure gauge to the fuel rail.
• Turn the ignition to the "ON" position without starting the engine and check the fuel pressure; it should typically be around 50-60 psi.
• If pressure is low, check the fuel filter and fuel pump for issues; replace as necessary.

5. Inspect for Vacuum Leaks

• Visually inspect all vacuum lines for cracks or disconnects.
• Use a smoke machine or carburetor cleaner to check for leaks around the intake manifold and vacuum connections.
• Repair or replace any damaged hoses or gaskets.

6. Compression Test

• Remove the spark plugs again to reduce resistance while testing.
• Insert a compression tester into each cylinder and crank the engine.
• Compare readings; they should be within manufacturer specifications (usually 130-180 psi). If any cylinder reads significantly lower, investigate further for possible head gasket or valve issues.